Three-fold mirror assembly for a scanning projection system

In an apparatus for photographically exposing an image receiving surface to a light image of an object, said apparatus comprising a unit power optical system having an optical axis and having conjugate planes normal to that axis for which the system is of unit power,

• plane reflecting surfaces interposed in the optical system for repositioning said conjugate planes,
• separate means to support substantially plane object and image-receiving surfaces in said repositions of the conjugate planes, and
• means to illuminate in said object surface an arcuate area exterior of and having its center of curvature substantially on said optical axis in relation to said reposition of the object plane,
• said plane reflecting surfaces comprising a first plane reflecting surface at an angle to said optical axis for repositioning one of said conjugate planes and
• a 90.degree. roof formed of a pair of plane reflecting surfaces having their line of intersection at a 90.degree. angle relative to the plane of the first plane reflecting surface, and said roof being disposed for locating said other conjugated plane parallel to said one conjugate plane to permit advancing said object and image surfaces in the same direction simultaneously and for said reflecting surfaces to generate at said image surface an image equivalent in orientation to a contact print image.